\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,xscale=0.8]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw [->](-2,0)--(6,0)node[right]{$\omega t$};
  \draw [->](0,-1.5)--(0,1.5)node[right]{$i$};
  \draw [ultra thick] plot[domain=0:5.3, samples=1000] function{sin(x+1)} ;
  \draw [ultra thick, dashed] plot[domain=-1:0, samples=100] function{sin(x+1)};
  \node at (2,1) [below]{$i_1$};
  \draw [very thick] plot[domain=0:5.3, samples=1000] function{-.7*sin(x+1)} ;
  \draw [very thick, dashed] plot[domain=-1:0, samples=100] function{-.7*sin(x+1)};
  \node at (1,-.55)[below]{$i_2$};
  \draw [dashed] (-1,0)--(-1,-1.5);
  \draw [<->] (0,-1)--node[above]{$\phi_0$}(-1, -1);
\end{tikzpicture}
\end{document}